Optical recording medium, recorder for optical recording medium, method for recording the same, reproducing device and reproducing method therefor

ABSTRACT

In an optical recording medium having a track including plural pits formed based on first data to be recorded and lands defined between neighboring pits, these pits are recorded as they are deformed based on the second data. The first and second data are synthesized and reproduced to realize audio reproduction with a broad frequency range. Moreover, the first data are adapted to be reproducible by a customary disc reproduction device. The reproduction of the first data is controlled by the second data to protect recorded data.

TECHNICAL FIELD

This invention relates to an optical recording medium having recordedthereon second data, as supplementary data, in addition to first data asmain data, a recording method and apparatus for recording thesupplementary data along with the main data on this optical recordingmedium and a method and apparatus for reproducing an optical recordingmedium having the first and second data recorded thereon.

More particularly, this invention relates to an optical recording mediumin which the shape of plural pits of a track comprised of the pitsrepresenting recording data and lands between these pits is deformed torecord other data, a recording method and apparatus for recording dataon the optical recording medium and to a method and apparatus forreproducing the optical recording medium.

BACKGROUND ART

Up to now, an optical disc, such as a compact disc with a diameter equalto 12 cm, is widely employed as an optical recording medium havingrecorded thereon audio data, such as music numbers.

In recording on this optical disc, audio data is sequentially blockedand added to with an error correction code. The resulting data ismodulated with EFM (eight to fourteen modulation), with the results ofthe modulation being recorded by NRZI (non-return-to-zero inverted)modulation. On the compact disc, audio data is recorded by repetition ofpits and lands with nine different lengths of the periods of 3T to 11T,where T is the basic period equal to the channel clock period.

The pits formed in the optical disc based on the recorded audio data areof length in the track direction equal to approximately 0.87 to 3.18 μm,in association with the periods of 3T to 11T, with the pit widthcorresponding to the length in a direction perpendicular to the trackdirection being approximately 0.5 μm, with its depth being approximately0.1 μm.

Meanwhile, in a compact disc, audio data is recorded in a frequencyrange of 20 Hz to 20 kHz. However, a demand is raised to enable audiodata to be recorded over a broader frequency range to realize audioreproduction of a higher sound quality. There is also raised a demandfor recording audio data of three or more channels, instead of twochannels, that is left and right channels, to enable variegated audioreproduction, such as surround reproduction.

Moreover, there is raised a demand for enabling audio data recorded onan optical disc to be reproduced only under a pre-set condition toprotect the recorded audio data.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide an optical recordingmedium enabling variegated audio reproduction by recording supplementarydata in addition to main data, a method and apparatus for recording dataon this optical recording medium and a method and apparatus forreproducing the optical recording medium.

It is another object of the present invention to provide an opticalrecording medium which enables at least main data to be reproduced usinga customary optical disc player and on which has been recordedsupplementary data in addition to the main data, and a method andapparatus for recording data on this optical recording medium.

It is still another object of the present invention to provide anoptical recording medium which enables recording of audio data of afrequency range broader than that of the customary compact disc ormulti-channel audio reproduction to a high sound quality, and a methodand apparatus for recording data on this optical recording medium.

It is yet another object of the present invention to provide an opticalrecording medium which enables reliable protection of recorded data anda method and apparatus for recording data on this optical recordingmedium.

For accomplishing the above object, the present invention provides anoptical recording medium including a track constituted by a plurality ofpits formed based on first data recorded therein and lands definedbetween the pits, wherein the plural pits are deformed based on seconddata.

The present invention also provides a recording apparatus for an opticalrecording medium including an objective lens for converging a recordinglaser beam outputted by a modulator for modulating the recording laserbeam radiated by a light source for radiating the recording laser beambased on the furnished first data and second data to the opticalrecording medium. This recording apparatus includes a signal processorfor generating first data based on main data recorded on the opticalrecording medium and for generating second data based on supplementarydata of the main data recorded on the optical recording medium.

The present invention also provides a reproducing apparatus for anoptical recording medium, the apparatus including an optical pickup forreading out first and second data from an optical recording mediumincluding a track formed by a plurality of pits formed based on thefirst data recorded therein and a land defined between neighboring pits,with the pits being deformed based on the second data, a firstdemodulator for demodulating the first data of the optical recordingmedium based on an output signal of the optical pickup, and a seconddemodulator for demodulating the second data of the optical recordingmedium based on the output signal of the optical pickup. The seconddemodulator includes a demodulation processor for demodulating an outputof the signal level discriminating portion adapted for discriminatingthe signal level of the playback signal supplied from the signalprocessor.

Preferably, the reproducing apparatus also includes a synthesizingportion for synthesizing an output signal of the first demodulator andan output signal of the second demodulator. The reproducing apparatusalso includes an external equipment discriminating portion fordiscriminating whether or not an external equipment connected to theapparatus is an authentic external equipment. Tile reproducing apparatusoutputs at least an output signal of the second modulator when the anexternal equipment connected to the apparatus is discriminated by theexternal equipment discriminating portion to be an authentic externalequipment.

The optical pickup preferably includes a photodetector split in thetrack direction of the optical recording medium at least into a firstphotodetector portion and a second photodetector portion. The apparatusalso includes a signal processor for processing output signals of thefirst and second photodetector portions. The first demodulator is fedfrom the signal processor with a sum signal representing the sum ofoutput signals of the first and second photodetector portions, whilstthe second demodulator is fed from the signal processor with adifference signal representing the difference between output signals ofthe first and second photodetector portions.

The present invention also provides a reproducing apparatus for anoptical recording medium including an optical pickup for reading outfirst and second data and discriminating data from an optical recordingmedium including a track formed by a plurality of pits formed based onthe first data recorded therein and a land defined between neighboringpits, with the pits being deformed based on the second data. The opticalrecording medium also has the discriminating data recorded thereon. Thereproducing apparatus for an optical recording medium also includes afirst demodulator for demodulating the first data of the opticalrecording medium based on an output signal of the optical pickup, asecond demodulator for demodulating the second data of the opticalrecording medium based on the output signal of the optical pickup and acontroller for controlling the operation of the second demodulator basedon the discriminating data read out by the optical pickup from theoptical recording medium.

The present invention also provides an optical recording mediumincluding a data recording area having a spirally extending trackconstituted by a plurality of pits formed based on first data recordedtherein and lands defined between neighboring pits, and a managementdata area for recording therein management data for the first datarecorded in the data recording area. At least the plural bits recordedin the management area are previously deformed based on the second data.

Preferably, the first data is digital data recorded on the opticalrecording medium, whilst the second data is supplementary data to thedigital data. The supplementary data is data at least includingcopyright data.

Preferably, the first data is upper bits of digital data recorded on theoptical recording medium, whilst the second data is lower bits of thedigital data.

In the management data area, there is preferably recorded discriminatingdata indicating whether or not the second data is recorded on theoptical recording medium.

Preferably, the first data recorded on the optical recording medium isencrypted, whilst the second data is recorded as key data for decryptingthe first data.

The present invention also provides a method for recording an opticalrecording medium including modulating a recording laser beam outputtedby a light source with furnished first and second data, converging themodulated recording laser beam on an optical recording medium through anobjective lens for forming a track including at least a plurality ofpits derived from the first data and lands defined between the pits anddeforming the pits formed on the optical recording medium based on thesecond data. The first data is generated based on the main data recordedon the optical recording medium, whilst the second data is generatedbased on the supplementary data to the main data recorded on the opticalrecording medium.

The present invention also provides a method for reproducing an opticalrecording medium including reading out first and second data from anoptical recording medium including a track formed by a plurality of pitsformed based on the first data recorded therein and a land definedbetween neighboring pits, the pits being deformed based on the seconddata, demodulating the first data of the optical recording medium basedon an output signal of data read out from the optical recording mediumand demodulating the second data based on playback signals of data readout from the optical recording medium.

Preferably, the signal level of the playback signals read out from theoptical recording medium is discriminated to demodulate the second data.

Preferably, the demodulated first and second data are synthesizedtogether and outputted.

In this reproducing method, at least demodulated second data preferablyis outputted and reproduced when an external equipment connected to areproducing apparatus is discriminated to be an authentic externalequipment.

The present invention also provides a reproducing method for an opticalrecording medium including demodulating first data based on playbacksignals of data read out from an optical recording medium including atrack made up of a plurality of pits formed based on the first datarecorded and lands defined between neighboring pits, with the pluralbits being deformed based on second data, with the optical recordingmedium having discriminating data recorded thereon, and demodulating thesecond data based on playback signals of data read out from the opticalrecording medium based on the results of discrimination of thediscrimination data read out from the optical recording medium. If thediscriminating data recorded on the optical recording medium indicatesthat the second data has been recorded on the optical recording medium,the second data is demodulated based on the data read out from theoptical recording medium.

Other objects and advantages of the present invention will becomeapparent from the following description which is ma de with reference tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a recording apparatus for an opticaldisc according to the present invention.

FIGS. 2A to 2D are diagrammatic views showing the structure of a trackin which are formed pits formed in an optical disc prepared by therecording apparatus according to the present invention.

FIG. 3 is a block diagram showing a disc reproduced device used forreproduced an optical disc according to the present invention.

FIGS. 4A and 4B show playback data reproduced by the disc reproducingapparatus shown in FIG. 3.

FIGS. 5A to 5D show the structure of a track containing pits formed inan optical disc reproduced by the disc reproducing apparatus shown inFIG. 3.

FIGS. 6A to 6D show the structure of a track containing pits formed inan optical disc according to a second embodiment of the presentinvention.

FIGS. 7A and 7B are plan views showing the structure of pits formed inan optical disc according to a fourth embodiment of the presentinvention.

FIGS. 8A and 8B are plan views showing the structure of pits formed inan optical disc according to a sixth embodiment of the presentinvention.

FIGS. 9A and 9B are plan views showing the structure of pits formed inan optical disc according to a seventh embodiment of the presentinvention.

FIGS. 10A and 10B are plan views showing the structure of pits formed inan optical disc according to an eighth embodiment of the presentinvention.

FIG. 11 is a block diagram showing a photodetector constituting anoptical pickup used in a disc reproducing apparatus according to thepresent invention.

FIGS. 12A to 12E are plan views showing the structure of pits formed inan optical disc according to a ninth embodiment of the presentinvention.

FIGS. 13A and 13B are plan views showing the structure of pits formed inan optical disc according to a tenth embodiment of the presentinvention.

FIGS. 14A and 14B are plan views showing the structure of pits formed inan optical disc according to an eleventh embodiment of the presentinvention.

FIG. 15 is a plan view showing the structure of pits formed in anoptical disc according to a further embodiment of the present invention.

FIG. 16 is a plan view showing how a maid portion in the longitudinaldirection of a pit formed in an optical disc according to the presentinvention has been deformed into second data.

FIG. 17 shows a playback output obtained on reproducing the optical discshown in FIG. 16.

FIG. 18 is a perspective view showing an optical disc according to thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to the drawings, an optical recording median, a recordingmethod and apparatus for recording the optical recording medium and amethod and apparatus for reproducing an optical recording medium arehereinafter explained in detail.

(1) Recording Apparatus

A recording device for recording data on an optical recording mediumaccording to the present invention is first explained.

This recording device is used for fabricating an optical disc as anoptical recording medium according to the present invention. Forfabricating the optical disc according to the present invention, amaster disc 2, exposed to light by the recording device 1 shown in FIG.1, is developed and processed with electroforming to produce a motherdisc, which then is used for producing the optical disc. In forming theoptical disc, a stamper is formed from a mother disc and a metal molddevice carrying this stamper is used to mold a disc substrate. Areflective film then is deposited on the molded disc substrate todeposit a reflective film.

A master disc 2, exposed to light using the recording device shown inFIG. 1, is prepared by coating a light sensitizer on a flat glasssubstrate. The master disc 2 is loaded on a spindle motor 3 and run inrotation at a constant rpm by the spindle motor 3 being drivenrotationally under control by a spindle servo circuit 4. At this time,the spindle motor 3 generates an FG signal FG the signal level of whichrises at an interval of a pre-set rotational angle by an FG signalgenerator provided on its bottom. The spindle servo circuit 4 drives thespindle motor 3 so that the FG signal FG will be of a pre-set frequency,thereby causing the master disc 2 to run in rotation at a constantlinear velocity.

A recording laser 5 is constructed by e.g., a gas laser, and radiates alaser beam of a pre-set light volume. A light modulator 6 is constitutedby an electro-acoustic optical element and is adapted for intensitymodulating the laser beam L incident from the recording laser 5 inkeeping with a driving signal S3 to raise this laser beam Lintermittently responsive to the rise of the signal level of the drivingsignal S3. The light modulator 6 changes the light volume of the laserbeam L, raised in this manner, responsive to the signal level of thedriving signal.

A mirror 8 warps the light path of the laser beam L to radiate the lighttowards the master disc 2. An objective lens 9 converges the reflectedlight of the mirror 8 onto the recording surface of the master disc 2.The mirror 8 and the objective lens 9 are sequentially fed in the radialdirection of the master disc 2, by a sled mechanism, not shown, insynchronism with rotation of the master disc 2. As the mirror 8 and theobjective lens 9 are fed, the optical disc recording device 1sequentially displaces the light converging position of the laser beam Lfrom the inner rim towards the outer rim of the master disc 2 to form aspirally or concentrically extending track on the master disc 2. At thistime, a pit string made up of plural pits corresponding to modulatingsignals is formed on this track. This pit string is modulated in widthby the modulating signal S3.

An analog/digital (A/D) conversion circuit 10 analog/digital converts anaudio signal SA supplied from a pre-set music source to output 18-bitparallel audio data DA having the sampling frequency DA of 44.1 kHz.

A bit operating unit 11 splits the 18-bit parallel audio data DA intoupper-order 16-bit first data D2U and lower-order 2-bit second data D2L.The first data D2U corresponds to audio data recorded on a customarycompact disc. The second data D2L is the supplementary data to the firstdata D2U and may, for example, be audio data of the high frequency rangenot contained in the first data D2U.

A data processing circuit 12 is fed with TOC (table-of-contents) data,recorded on a lead-in area of an optical disc, and processes this TOCdata in accordance with the format prescribed for a customary compactdisc. This permits the data processing circuit 12 to generate and outputchannel data corresponding to the bit string.

To the TOC data, thus recorded, there are allocated disc discriminationdata ID indicating that the optical disc has recorded thereon audio dataD2L containing second data D2U as audio data of the high frequency rangeand copy discrimination data IC indicating that the optical disc is anoriginal optical disc prepared from a mother disc. By recording thediscrimination data ID, it becomes possible to detect the discriminationdata ID at the time of reproduction to render it possible to reproduceaudio data DA, processed as upper 16 bits and lower 2 bits, based on thedetected results. It is also possible to discriminate, based on the copydiscrimination data IC, whether or not the optical disc is onecomprising audio data DA copied from an original optical disc.

In a similar manner, the data processing circuit 12 processes the firstdata D2U, outputted from the bit operating unit 11, in accordance withthe format prescribed for the customary compact disc, to generate andoutput channel data D3 corresponding to the pit string. The channel dataD3 corresponding to the pit string is generated and outputted. That is,the data processing circuit 12 appends an error correction code to thefirst data D2U to interleave the resulting data to EFM to demodulate theprocessed results. In this EFM modulation, the data processing circuit12 generates 14 channel bits by periods 14 times the basic period T,from each byte of the first data D2U, as shown in FIG. 2A, and connectsbye 14-bit data with 3 connecting channel bits. The data processingcircuit 12 NRZI-modulates this serial data string to generate channeldata D3, as shown in FIG. 2B. Meanwhile, in the customary compact disc,the laser beam L is on/off controlled responsive to the channel data D3to produce a pit string with a pit width of 0.5 μm.

Moreover, the data processing circuit 12 performs processingcorresponding to the processing unit of the first data D2U of theupper-order 16 bits to add an error correction code to the lower 2-bitsecond data D2L. The data processing circuit 12 then interleaves theresulting data to convert the interleaved data into serial data. At thistime, the data processing circuit 12 appends an error correction code byapplying 4-bit-based simply parity. That is, the data processing circuit12 collects audio data made up of the upper order first data D2U and thelower order second data D2L, in terms of 4 bits as a unit, to generate ablock composed of six data (24 bits) to append a 4-bit parity to eachblock. The data processing circuit 12 interleaves each block comprisingthe six data (24 bits) and a single parity (4 bits) and appends a 4-bitparity to the interleaved block.

The data processing circuit 12 converts the so-generated pit string intoa serial data string. Also, for the time period since conversion of thelogical level of the channel data D3 to a logical level corresponding tothe pit until its conversion to a logical level corresponding to theland formed between the pits, the data processing circuit 12 generatesand outputs light volume control data D4 which sequentially allocatesthe bits of the serial data.

A driving circuit 13 receives the channel data D3 outputted by the dataprocessing circuit 12 to generate a driving signal S3 the signal levelof which intermittently raises the laser beam L in association with thelogical level of this channel data D3.

With the recording device 1, the upper 16 bits of the 18 bits making upthe audio data DA supplied to this device 1 are recorded as a pit stringmade up of plural pits P₁ on the master disc 2 so that the upper 16 bitswill be reproduced by a disc reproducing device adapted for reproducingthe customary compact disc.

The driving circuit 13 intermittently raises the light bean L by a lightvolume control data D4 to generate the driving signal S3 so that a widthW₂, equal to the length in a direction perpendicular to the trackdirection, will be varied so as to be narrower than a normal width W₁responsive to the light volume control data D4. This records the seconddata D2L, recorded on the optical disc, as variation in the width whichis the length of the pit in a direction perpendicular to the trackdirection.

When the light volume control data D4 is recorded by the pit width inthis manner, the peak value or the bottom value is changed responsive tothe light volume control data D4. In the present example, the pit widthis modulated with 0.5±0.1 μm, so that, even if the peak or bottom valueis changed as shown in FIGS. 2A to 2D, the 16-bit first data D2U will bereproduced with a sufficient amplitude allowance in a disc reproducingapparatus dedicated to reproduction of the customary compact disc.

(2) Disc Reproducing Apparatus

A disc reproducing apparatus enabling selective reproduction of theoptical disc having recorded data thereon and the routine compact disc,according to the present invention, will hereinafter be explained.

When the optical disc 21 is loaded on the disc reproducing apparatus 20,as shown in FIG. 3, the present disc reproducing apparatus 20rotationally drives the optical disc 21 under a constant linear velocityby a spindle motor 22 with the reproducing signal RF obtained from theoptical pickup 23 as a reference.

The optical pickup 23, employed in this disc reproducing apparatus 20,illuminates a light beam on the optical disc 21 by an enclosedsemiconductor laser used as a light source to receive the return lightbeam reflected from the optical disc 21 by a pre-set light receivingelement. The optical pickup 23 outputs a playback signal RF the signallevel of which is changed responsive to the intensity of the returnlight beam received by the light receiving surface of the lightreceiving element. The reproducing signal RF is changed in signal levelresponsive to a pit P₁ and a land R₁ formed on the optical disc 21,while being changed in peak or bottom value in dependence upon the widthof the pit formed on the optical disc 1.

The RF circuit 24 amplifies the reproducing signal Rf at a pre-set gainto output the resulting reproducing signal Rf. In the initial state, aselection circuit 25 outputs the reproducing signal Rf, outputted bythis RF circuit 24, to an EFM (8-14) demodulating circuit 26. However,if a disc discriminating circuit 27 detects that the loaded optical disc21 is the optical disc having recorded thereon not only the first dataD2U but also the second data D2U, according to the present invention,the selection circuit 25 outputs the reproducing signal Rf to an RFlevel discriminating circuit 28 under control by the disc discriminatingcircuit 27.

If the loaded optical disc 21 is the customary optical disc 21, the EFMdemodulating circuit 26 bi-level-discriminates the reproducing signal Rfoutputted by the RF circuit 24 to generate playback data. The EFMdemodulating circuit 26 also EFM demodulates the playback data to outputthe demodulated data. If conversely the disc discriminating circuit 27detects that the loaded optical disc 27 is the optical disc according tothe present invention, the EFM demodulating circuit 26 EFM-demodulatesplayback data outputted by the RF level discriminating circuit 28, undercontrol by the disc discriminating circuit 27, to output the demodulateddata. Meanwhile, the EFM demodulating circuit 26 outputs playback datacorresponding to the repetition of pits and lands, no matter whether theloaded optical disc 21 is an optical disc according to the presentinvention or a customary compact disc.

A CIRC decoder 29 descrambles output data of the EFM demodulatingcircuit 26 and corrects the output data for errors by the errorcorrection code appended in recording, to reproduce and output audiodata D4. With the disc reproducing apparatus 20 according to the presentinvention, the audio data D4 is outputted in 16 bits, no matter whetherthe loaded optical disc 21 is a customary compact disc or an opticaldisc according to the present invention, in the same way as in signalprocessing in the disc reproducing device dedicated to reproduction of acustomary compact disc. Directly after loading the optical disc 21, thereproducing signal Rf may be processed in a similar manner whereby thevariable information recorded in a lead-in area of the optical disc 21may be reproduced and outputted to a system controller including thedisc discriminating circuit 27.

Similarly to the EFM demodulating circuit 26, the RF leveldiscriminating circuit 28 bi-level-discriminates the reproducing signaloutputted by the RF circuit 24 to generate playback data to output theplayback data to the EFM (8-14) demodulating circuit 26. The reproducingsignals Rf are derived from the optical disc 21 according to the presentinvention, in which the pit width W is modulated by the second data D2L,so that the peak or bottom value is changed in the reproducing signal Rfwith the pit width W, as shown in FIGS. 4A and 4B.

If the pit width W₁ is 0.6 μm for the quality improving data value oflogic 1, with the pit width W₂ being 0.6 μm for the quality improvingdata value of logic 0, the bottom value of the reproducing signal Rf isB_(H) and B_(L) for the pit width W₁ of 0.6 μm and 0.4 μm, as shown forexample in FIG. 4B, respectively.

In this manner, the RF level discriminating circuit 28 corrects thethreshold value discriminating the first data D2U tobi-level-discriminate the reproducing signal Rf, so that the result ofbi-level discrimination will not be affected even if the peak value orthe bottom value of the reproducing signal Rf is changed. The RF leveldiscriminating circuit 28 sequentially detects the level of the peakvalue B_(H) or the bottom value B_(L) of the reproducing signal Rf tosequentially detect the signal level of the reproducing signal Rf at thecenter of each pit. On the other hand, the RF level discriminatingcircuit 28 corrects the results of the signal level detection by the pitlength of the first data D2U obtained on bi-level discrimination tonormalize the results of signal level detection responsive only to thepit width.

That is, with the pit length of a period approximately equal to or lessthan 4T, the reproducing signal Rf, modulated based on the second dataD2L, has its peak or bottom value changed with the period, such that, ifthe pit length is equal to or longer than 5T, the peak or bottom valueshows a saturated value, that is the level B_(L). The RF leveldiscriminating circuit 28 multiplies the result of signal leveldetection with a pre-set constant consistent with the length of the pitP₁ in the first data D2U. Specifically, the RF level discriminatingcircuit 28 multiplies the result of signal level detection with apre-set constant proportionate to the length of the pit P₁ in the firstdata, such as 1 when the pit length is of the period not less than theperiod 5T or a constant inversely proportionate to the pit length whenthe pit length is not less than the period 4T. Specifically, the level Xof the reproducing signal Rf corresponding to the pit length shown inFIG. 4B is normalized to the level B_(L). The RF level discriminatingcircuit 28 outputs the result of the normalized signal level detectionresults DP to a bi-level demodulation circuit 30.

The bi-level demodulation circuit 30 bi-level-discriminates thenormalized signal level detection results DP based on a pre-setthreshold value, for example, an intermediate level THL between thelevel B_(L) and the level B_(H) to reproduce second data. Specifically,the bi-level demodulation circuit 30 outputs 1 or 0 as second data whenthe signal level detection results DP is lower or higher than athreshold value THL, respectively.

An ECC decoder 31 corrects payback data outputted by the bi-leveldemodulation circuit 30 for errors and de-interleaves the resulting datato reproduce and output 2-bit second data D2L(D6). If the loaded opticaldisc 21 is a customary compact disc, and the audio data D6 is processedwith exclusive-OR in a mixer 35 as later explained, 2-bit logic “00”data is outputted in place of the 2-bit second D2L. If the audio data D6is processed with multiplication in the mixer 35, a 2-bit data string bypre-set random number data is sequentially outputted.

A multiplexer (MUX) 33 appends 2-bit parallel second data D2L outputtedby the ECC decoder 31 to the lower bit side of the 16-bit parallel firstdata D2U outputted by the CIRC decoder 29 to output 18-bit parallelaudio data. This permits the multiplexor (MUX) 33 to output audio dataDAEx, capable of reproduced the high sound quality with a broadfrequency range, provided that the optical disc 21 is an optical discaccording to the present invention.

A mixer (MIX) 35 processes the lower two bits of the 16-bit parallelaudio data, outputted by the CIRC decoder 29, with each bit of thesecond data D2L, outputted by the ECC decoder 31, by exclusive-OR, tooutput audio data DB of a narrow frequency range not containing thesecond data D2L outputted by the CIRC decoder 29. If data by randomnumber is to be outputted by the ECC decoder 31, the mixer 35 multipliesthe lower two bits of the audio data with the random number data tooutput audio data DB not containing the second data D2L.

The disc discriminating circuit 27 is constituted by a systemcontroller, which, when the optical disc 21 is loaded, performs a seekoperation of scanning the inner and outer rims of the optical disc 21 ata high speed, by way of seeking, to acquire the information concerningthe number of musical air s or the playing time, recorded on the opticaldisc 21, to demonstrate the acquired information on pre-set displaymeans. The system controller also acquires disc discrimination data IDof the optical disc 21 to verify whether the optical disc 21 is thecustomary compact disc or an optical disc according to the presentinvention, in accordance with the disc discrimination data ID. The discdiscriminating circuit 27 controls the switching of the contacts of theselection circuits 25, 26 based on the discriminated results.

If, s a result of check obtained on reproducing the data recorded in alead-in area of the optical disc 21, the disc discriminating circuit 27has verified that the loaded optical disc 21 is the optical discaccording to the present invention, the disc discriminating circuit 27processes the reproducing signal Rf outputted by the RF circuit 24 bythe RF level discriminating circuit 28 to reproduce the audio data DAExof the wide frequency range containing the first data D2U and the seconddata D2L.

If the optical disc 21 is the customary compact disc, a selectioncircuit 36 selectively outputs the audio data D6, outputted by the CIRCdecoder 29, to a digital/analog (D/A) conversion circuit 37. Ifconversely the optical disc 21 is an optical disc having not only thefirst data D2U but also the second data D2L recorded thereon, inaccordance with the present invention, the selection circuit 36selectively outputs audio data of a wide frequency range, synthesizedfrom the first data D2U and the second data D2L outputted by themultiplexor 33.

The digital/analog conversion circuit 37 digital-to-analog converts theaudio data outputted by the selection circuit 36 to output audio data SAby analog signals. Thus, with the playback sound quality by analogsignals, if the disc is the customary compact disc, the disc reproducingapparatus 20 selectively processes the audio data D6 outputted by theCIRC decoder 29 to reproduce the sound with the sound quality equivalentto the conventional 16-bit sound quality, indicated as CD sound qualityin Table 1, whereas, if the disc is the optical disc 21 according to thepresent invention, the disc reproducing apparatus 20 selectivelyprocesses the 18-bit equivalent audio data DAEx of a broad frequencyrange, indicated as ExCD sound quality in Table 1, synthesized from thefirst data D2U and the second data D2L outputted by the multiplexor 33.

In a conventional disc reproducing apparatus, dedicated to reproductionof the customary compact disc, the audio data D6, outputted by the CIRCdecoder 29, is outputted without the intermediary of the mixer 35, sothat the conventional disc reproducing apparatus reproduces the audiodata recorded on the customary compact disc and on the optical disc ofthe present invention with the CD sound quality comparable to that ofthe customary compact disc.

TABLE 1 reproduced disc sound quality duplication on CD conventionaldisc CD disc CD sound quality CD sound quality reproducing ExCD disc CDsound CD sound quality apparatus quality inventive disc CD disc CD soundFM sound quality reproducing quality (CD sound quality) apparatus(conventional PC) CD sound quality (second duplication inhibited PC)ExCD disc ExCD sound FM sound quality quality (conventional PC) ExCDsound quality (CD sound quality) (second duplication inhibited PC)

An interface (I/F) 38 constitutes an input/output circuit fortransmitting/receiving variable data with an external equipment etc tooutput audio data to a personal computer in accordance with the SCMSformat or to transmit/receive variable data relevant to audio data.

Similarly to the disc discriminating circuit 27, an external equipmentdiscriminating unit 39 is constituted by a system controller of thepresent disc reproducing apparatus 20 and executes pre-set authorizationprocessing with an external equipment through an interface 38. In thisauthorization processing, the external equipment discriminating unit 39sends pre-set data to the external equipment and, subject to theresponse from the external equipment to this data, verifies whether ornot the computer connected to the interface 38 is an authentic equipmentwhich inhibits second duplication of the audio data recorded on theoptical disc 1 to protect the copyright.

The equipment which protects the copyright is such an equipment havingthe function of inhibiting so-called second copying by re-duplicating awhole copy once obtained from data containing the audio data recorded onthe optical disc. If the external equipment is a personal computer andan optical disc which has duplicated tile audio data outputted from thedisc reproducing apparatus 20 is to be prepared, this personal computeris the equipment protecting the copyright if it has the function ofcorrectly setting the duplication discriminating data IC. This computeris shown in Table 1 as being a second duplication inhibiting PC incontradistinction from a conventional personal computer

A selection circuit 40 operates, based on the results of discriminationof the external equipment discriminating unit 39, so that, if theexternal equipment is an authentic equipment inhibiting secondduplication of audio data recorded on the optical disc, the selectioncircuit 40 selectively outputs audio data outputted by the selectioncircuit 36, whereas, if the external equipment is not an equipment nothaving the function of inhibiting second duplication of audio data, theselection circuit 40 selectively outputs audio data DB outputted by themixer 35. Thus, if the external equipment is an authentic equipmentinhibiting second duplication, and the optical disc 21 is a customarycompact disc, the selection circuit 40 outputs audio data of the 16-bitequivalent sound quality, whereas, if the optical disc 21 is thecustomary compact disc or the optical disc according to the presentinvention, only data corresponding to the first data D2U having the16-bit equivalent sound quality may be outputted. For a customarycompact disc, audio data by the 16-bit equivalent sound quality may beoutputted, as in the conventional equipment. The sound quality in suchcase is indicated as the FM sound quality in Table 1.

Meanwhile, if the external equipment is an authentic equipmentinhibiting second duplication, the present disc reproducing apparatus 20is able to switch the contacts of the selection circuit 36 in aninterlocked relation to the selection circuit 40 to output 16-bitequivalent audio data equivalent to the audio data recorded on thecustomary compact disc.

(3) Data Recording Operation and Audio Reproducing Operation by aRecording Device

For producing an optical disc according to the present invention, usingthe recording device 1, shown in FIG. 1, the audio signals SA forrecording, supplied to the recording device 1, is converted by ananalog/digital conversion circuit 10 into 18-bit audio data DA, whichaudio data DA is split by the bit operating unit 11 into the first dataD2U by upper 16 bits and the second data D2L by the lower 2 bits. To thefirst data D2U by the upper 16 bits, an error correction code isappended in the same way as in preparing the customary compact disc, bythe data processing circuit 12. The resulting data is interleaved andmodulated by EFM. The 14-channel bit data by the EFM modulated data,produced as described above, are connected by connecting bits of 3channel bits to generate channel data D3. The first data D2U by theupper 16 bits are recorded on the optical disc as a repetition of pitsP₁ and lands R₁, by the light beam L being turned on and off by thechannel data D3 to sequentially expose the master disc 2 to light.

The first data D2U, made up of upper 16 bits, is recorded on the opticaldisc as data reproducible by the disc reproducing device adapted forexclusively reproducing the customary compact disc.

On the other hand, the audio data D2L of the lower 2 bits are collectedin terms of 4 bits as a unit as audio data of the frequency range higherthan that of the first data D2U to form a block composed of six data (24bits). A 4-bit parity is appended to each block. Each block composed of6 data (24 bits) and a single parity (4 bits) are interleaved and a4-bit parity is appended to the interleaved data.

The audio data D2L of the lower 2 bits, to which the error correctioncode has been appended as described above, are interleaved andsubstantially converted into serial data D4. The serial data then isallotted to pits so that each bit of the serial data D4 is inassociation with one pit. The light volume of the light beam L isswitched depending on the logical level of the serial data during thetime period the master disc 2 is exposed to light. In this manner, thesecond data D2L, which enlarges the playback frequency range by thelower two bits, is sequentially recorded on the optical disc by changesin the pit width W, as shown in FIGS. 2A to 2D.

In exposing the master disc 2 to light in this manner, a lead-in area isformed by TOC data outputted by a pre-set server. By the discdiscrimination data ID, allotted to the TOC data, it is possible todiscriminate whether the optical disc is an optical disc in which 18-bitaudio data has been split into the upper 12 bits and the lower 2 bits,or a customary compact disc. Similarly, by the copy discrimination dataIC, it is similarly possible to discriminate whether the optical disc isan original optical disc or an optical disc on which audio data has oncebeen duplicated.

With the optical disc 21, thus prepared, playback signals detected bythe optical pickup 23 are amplified by an RF circuit 24 and demodulatedby the EFM demodulating circuit 26 to generate playback data which thenis descrambled and corrected for errors to reproduce 16-bit audio dataD6.

In a disc reproducing apparatus for reproducing the customary compactdisc, the audio data D6 outputted by the CIRC decoder 29 is outputted toan external equipment, while being outputted as converted analogsignals. In this manner, 16-bit audio data is outputted directly or asconverted analog signals, when the customary compact disc is loaded on adisc reproducing apparatus adapted for exclusively reproducing thecustomary compact disc, or when an optical disc having recorded thereonthe first data D2U and the second data D2L according to the presentinvention is loaded thereon.

An optical disc according to the present invention can also bereproduced by a disc reproducing apparatus adapted for exclusivelyreproducing the customary compact disc, thus assuring lowercompatibility with respect to the disc reproducing apparatus adapted forexclusively reproducing the customary compact disc.

In the disc reproducing apparatus 20 capable of reproducing the opticaldisc according to the present invention, the disc discrimination data IDis detected from the TOC data of the lead-in area. From this discdiscrimination data ID, it can be discriminated whether the loadedoptical disc 21 is the customary compact disc or the optical discaccording to the present invention.

When the customary compact disc is loaded, the 16-bit audio data D6outputted by the CIRC decoder 29 is inputted to the digital/analogconversion circuit 37 through the selection circuit 36 where the audiodata is converted into audio signals SA by analog signals. Thus, whenthe customary compact disc is loaded on the disc reproducing apparatus20, audio signals are reproduced with the 16-bit equivalent soundquality, as conventionally.

When the optical disc, having recorded thereon the first data D2U andtile second data D2L, is loaded, the reproducing signal Rf outputted bythe reproducing signal Rf is inputted through the selection circuit 25to the RF level discriminating circuit 28 where the playback data by therepetition of pits and lands are detected. The playback data isprocessed in a similar manner to the case of processing the playbackdata of the customary compact disc to output the 16-bit first data D2Ufrom the CIRC decoder 29.

In the RF level discriminating circuit 28, the peak or bottom value ofthe reproducing signal Rf corresponding to the mid point of the pit isdetected. From the result of the signal level detection, by this peak orbottom value, the variation by the pit length is corrected, and theresult of signal level detection DP, represented by changes in thesignal level with the pit width, is detected. The result of signal leveldetection DP is bi-level discriminated and playback data by the seconddata D2L of the lower two bits is detected, as shown in FIGS. 4A and 4B.This playback data is corrected for errors by the ECC decoder 31 anddeinterleaved and the second data D2L of the lower 2 bits is reproduced.In the multiplexor 33, the second data D2L of the lower 2 bits areappended to the lower side of the first data D2U of the upper 16 bits,outputted by the CIRC decoder 29, to generate the 18-bit audio data DAExof the broad frequency range. On the other hand, the second data D2L ismultiplied or EX-ORed in the mixer 35 with the lower two bits of theupper 16-bit first data D2U to generate 16-bit audio data DB of thefrequency range not containing the high frequency range.

In the disc reproducing apparatus 20 of the present invention, the audiodata DAEx of the broad frequency range containing the high frequencyrange is outputted by analog signals through the digital/analogconversion circuit 37 to reproduce the audio signals DAEx enabling theaudio reproduction of 18-bit equivalent high-quality signals.

When the disc reproducing apparatus 20 is to output the audio dataobtained from the customary compact disc, or the audio data obtainedfrom the optical disc according to the present invention, to an externalequipment, authorization processing is executed through the interface 38with the external equipment to verify whether or not the externalequipment is an equipment which disregards the code by the SCMS, such asthe customary personal computer. By this decision, it is verifiedwhether or not the external equipment connected to the disc reproducingapparatus 20 is an authentic equipment inhibiting second duplication. Ifthe external equipment is the authentic equipment inhibiting secondduplication, the audio data of the high frequency range containing thefirst data D2U and the second data D2L outputted by the multiplexor 33is outputted to the external equipment through the selection circuit 36,selection circuit 40 and the interface 38. If the loaded optical disc isthe customary compact disc, the 15-bit audio data, outputted by the CIRCdecoder 29, is outputted to the external equipment through the selectioncircuit 36, selection circuit 40 and the interface 38. In this manner,the audio data of the broad frequency range containing the highfrequency range is outputted to the external equipment. If this externalequipment is the authentic equipment inhibiting second duplication, theaudio data, once duplicated, cannot be duplicated further to prevent theprofits inherent to the copyright from being impaired by repeatedduplication.

If the external equipment connected to the disc reproducing apparatus 20is an equipment not having the function of inhibiting the secondduplication, audio data DB, deteriorated in sound quality by repeatedduplication of audio data a large number of times when outputted fromthe mixer 35, is outputted to the external equipment via the selectioncircuit 40 and the interface 38, such that, if copying of digitalsignals over an unlimited number of times is likely to be allowed, audiodata deteriorated in the sound quality is outputted, in such a mannerthat the merit of duplication by digital signals that repeatedduplication does not lead to deterioration in the sound quality is notexploited.

If the external equipment connected to the disc reproducing apparatus 20is such an equipment which has the function of inhibiting secondduplication, the copying discrimination data IC is set correctly for theduplication in which the audio data of the broad frequency rangecontaining the high frequency range inclusive of the first data D2U andthe second data D2L is outputted and prepared, so that, when the audiodata is reproduced by an equipment different from the present discreproducing apparatus 20, it is possible to prevent second duplicationof the audio data by e.g., the SCMS system, based on this copydiscrimination data IC, thereby protecting the profits accrued to thecopyright.

In the optical disc 21 of the present invention, in which plural bitsformed based on the first data D2U are deformed in width correspondingto the length in the direction perpendicular to the track direction,based on the second data D2L, and are recorded as the second data D2L.Therefore, if a misconception that the external equipment connected tothe disc reproducing apparatus 20 reproducing the optical disc 21 is theauthentic equipment having the function of inhibiting the secondduplication is willfully produced to output 18-bit audio data of thebroad frequency range containing the high frequency range inclusive ofthe first data D2U and the second data D2L, it becomes difficult to copythe entire audio data including the first data D2U and the second dataD2L to render it possible to prevent duplication of the audio data whichenables audio reproduction of the desired broad frequency range. Theresult is that repeated duplication of audio data enabling audioreproduction of high sound quality is prohibited to protect the profitsof the copyright owner by duplication.

With the optical disc according to the present invention, the audio dataDA by 18 bits is split into the first data D2U by the upper 16 bits andthe second data D2L by the lower 2 bits, the first data D2U by the upper16 bits is recorded by repetition of pits P₁ and lands R₁ between thepits P₁, while the second data D2L is recorded by lower two bits bychanges in the pit width, whereby it is possible to furnish high-qualityaudio signals enabling reproduction of the broad frequency rangecontaining the high frequency range as well as reproduction by a discreproduction apparatus adapted for exclusively reproducing the customarycompact disc. In addition, it is possible to prevent repeatedduplication of audio data DAEx enabling the high quality audioreproduction.

In addition, by discriminating whether or not the external equipmentconnected to the disc reproducing apparatus 20 has the function ofinhibiting the second duplication, and by outputting audio datacontaining only the first data D2U by the upper 16 bits or audio datacontaining both the first data D2U and the second data D2L, it ispossible to prevent repeated duplication of the audo data DAEx whichenables reproduction of the high sound quality audio signals.

Furthermore, if, in reproducing the optical disc according to thepresent invention by a disc reproducing apparatus, the audioreproduction obtained on reproducing the first data D2U by the seconddata D2L is rdeteriorated in sound quality, it is similarly possible toprotect the profits of the copyright owner by duplication of the audiodata DAEx which enables audio reproduction of desired high soundquality.

(4) Second Embodiment

In the present embodiment, as in the previous first embodiment, 18-bitaudio data is split into first data D2U of upper 16 bits and second dataD2L of lower 2 bits, the first data D2U of the upper 16 bits areprocessed identically as in the customary compact disc and recorded bylands R₁ between plural pits P₁, whilst the second data D2L of the lower2 bits are recorded by varying the length P_(L) in the track directionof the pit P₁ from the normal length.

In the present embodiment, the above-described recording device 1 andthe disc reproducing apparatus 20 may be used except recording thesecond data D2L on the optical disc by varying the width W which is thelength in the direction perpendicular to the track direction. Therefore,the recording device 1 and the disc reproducing apparatus 20 areexplained with reference to FIGS. 1 and 3, respectively.

In the recording device 1, used here, a data processing circuit 2appends an error correction code to the second data D2L of the lowerbits and interleaves the resulting data to generate a serial datastring, as in the first embodiment described above. The data processingcircuit 2 generates and outputs pit length control data D4, in whichrespective bits of the serial data are sequentially allotted to a timeperiod as from the time the logical level of a channel data D3 isswitched to the logical level corresponding to the pit until it isswitched to the logical level corresponding to the land.

A driving circuit 3 is fed with channel data D3, outputted from the dataprocessing circuit 2, and generates a driving signal S3, the signallevel of which corresponding to the logical level of the channel data D3rises intermittently. At this time, the driving circuit 3 drives amonovibrator by a pit length control data D4 and generates a drivingsignal S3 by the resulting timing signal and the channel data D3 so thatthe pit length will be changed depending on the logical level of the pitlength control data D4, with a time period sufficiently shorter than the½ period of the channel data D3, as shown in FIGS. 5A to 5D, as a unit.The variation of the pit length is set to enable processing of thereproducing signal Rf with a sufficient phase allowance even by a discreproducing device adapted for exclusively reproducing the customarycompact disc. In the present embodiment, the pit length variation is setso that the pit length will be varied by ±0.1 μm, depending on the pitlength control data D4, so that the pit length will be increased ordecreased about the length at the bit cell boundary as the referencelength as center.

By slightly changing the length P_(L1) in the track direction of the pitrecorded based on the first data D2U from the normal length P_(L), thesecond data D2L of the frequency range higher than the frequency rangeof the first data D2U is recorded on the optical disc.

If, when the optical disc 21, having recorded thereon the second dataD2L by slightly changing the length P_(L1) in the track direction of thepit P₁ from the normal length P_(L), is loaded on the disc reproducingapparatus and reproduced, the reproducing signal Rf isbi-level-discriminated with a pre-set threshold value, the time periodin register with the pit P₁ in which the signal level is decaying or thetime period in register with the pit P₁ in which the signal level isrising is varied depending on the logical level of the pit lengthcontrol data D4. Alternatively, in the reproducing signal level or thelogical level of the bi-level signal, obtained on sequentially samplingthe rising or falling edge of the bi-level signal, the signal level orthe logical level of a timing corresponding to the trailing edge of thepit P₁, with respect to the channel clock as a reference, is varieddepending on the logical level of the pit length control data D4. Thelength in the track direction of the pit P₁ in the optical disc 21 isslightly changed from its normal length, by time measurement of thebi-level signal or the logical level of the reproducing signal level orthe bi-level signal, with the clock signal as a reference, to reproducethe second data D2L.

Based on this detection principle, the RF level discriminating circuit28 and the a bi-level demodulation circuit 30 bi-level-discriminates thereproducing signal Rf, using channel clocks reproduced from thereproducing signal Rf as in the EFM demodulating circuit in the discreproducing apparatus configured for exclusively reproducing thecustomary compact disc, as a reference, to generate playback data, whiledetecting from the reproducing signal Rf the second data D2L enablingreproduction of a broad frequency range containing a frequency rangehigher than the reproducing signal Rf. That is, the RF leveldiscriminating circuit 28 binary-codes the reproducing signal Rf at apre-set threshold to generate bi-level signals and outputs timemeasurement results of the bi-level signals to the bi-level demodulationcircuit 30. Alternatively, the RF level discriminating circuit 28sequentially detects the signal level of the reproducing signal Rf orthe logical level of the bi-level signals, with the channel clocks asthe reference, and outputs, from the result of the detection, the resultof signal level detection DP or the result of logical level detection DPof a timing corresponding to the trailing edge.

The bi-level demodulation circuit 30 verifies the output results of theRF level discriminating circuit 28 to detect the playback data of thesecond data D2L containing the high frequency range.

With the optical disc 21 of the present embodiment, the results similarto those of the above-described first embodiment can be achieved if, byslightly changing the length in the track direction of a pit recordedbased on the first data D2U from its normal length, recording is made ofthe second data D2L of a frequency range higher than the frequency rangeof the first data D2U. By changing the length in the track direction ofthe pits by increasing/decreasing a length centered about the length upto a point corresponding to the pit cell boundary, the effect of jitterduring reproduction can be decreased to a practically sufficient level.

(5) Third Embodiment

With an optical disc 21 of the present embodiment, the 18-bit audio dataare split into upper 16-bit first data D2U and lower 2-bit second dataD2L, and the upper 16-bit first data D2U are processed as in thecustomary compact disc and recorded as a string of plural pits P₁, as inthe above-described first embodiment, whilst the lower 2-bit second dataD2L are recorded by varying the depth P_(D1) of the pit P₁ from thenormal depth P_(D).

In the recording device 1 used for preparing the optical disc 21, theresist is selected so that the degree of light exposure will be changedmainly in the depth-wise direction of the pit by changes in the lightvolume of the laser beam L.

By recording the second data D2L as the depth of pit formed in theoptical disc 21 is changed from the normal depth, the peak or bottomvalue is changed, responsive to the second data D2L, when the datarecorded on the optical disc 21 is reproduced, as in the firstembodiment described above. In the present embodiment, the second dataD2L is recorded as the depth is changed from the normal depth P_(D) to adepth P_(D1) by ±0.01 μm, so that, even when the peak or bottom value ischanged in this manner, audio data corresponding to the upper 16-bitfirst data D2U will be reproduced with a sufficient amplitude allowancein the disc reproduction apparatus used exclusively for reproducing thecustomary compact disc.

If the second data D2L is recorded as the depth of the pit P₁ is changedfrom the normal depth P_(D), the playback signals obtained onreproducing the optical disc 21 are changed in the peak or bottom valueresponsive to the second data D2L as in the first embodiment, so that itis possible to selectively process the audio data DAEx synthesized fromthe first data D2U and the second data D2L outputted by the multiplexor33 by the disc reproducing apparatus 20 of the present invention shownin FIG. 3 to make audio reproduction with the high sound quality (ExCDsound quality) covering the frequency range equivalent to 18 bits.

(6) Fourth Embodiment

With the present embodiment of the optical disc, similarly to theabove-described first embodiment, the upper 16-bit first data D2U of the18-bit audio data is processed in the same way as in the customarycompact disc and recorded as plural pits P₁, whilst the lower 2-bitsecond data D2L is recorded by changing a width W₃ of the pit which isthe length perpendicular to the length in the track direction of the pitP₁. By the pit width being changed with the second data D2L, a pit witha length longer than a pre-set length, such as a pit not shorter than5T, is selectively used, and a 1-bit data is allotted to the former andlatter halves from the center P₀ of the pit P₁ to change the pit widthW₄, as shown in FIGS. 7A and 7B.

The optical disc of the present embodiment is similar to the opticaldisc of the first embodiment, except the difference in timing inmodulating the pit width W₃. Therefore, the optical disc of the presentembodiment can be prepared, using the recording device 1 shown in FIG.1, while the optical disc can be reproduced using the disc reproducingapparatus 20 shown in FIG. 3.

In the recording device 1, an error correction code is appended to thelower 2-bit second data D2L and the resulting data is intereleaved toform a serial data string, by the data processing circuit 12, as in thefirst embodiment described above. The data processing circuit 12monitors tile logical level of a sustained pit P₁ in the channel data D3to detect the timing corresponding to the pit P₁ having a length notless than a pre-set length, such as 5T or longer. This data processingcircuit 12 allots each 1 bit data to the former and latter halves in thetrack direction of the pit not less than the pre-set length to generateand output the light volume control data D4.

In the disc reproducing apparatus 20 for reproducing the optical disc,shown in FIG. 3, the reproducing signal Rf is bi-level-discriminated,with the channel clocks regenerated by the reproducing signal Rf asreference, by signal processing similar to that performed by the EFMdemodulation circuit in the disc reproducing apparatus exclusivelyreproducing the customary compact disc, to generate playback data, whichis outputted to the EFM demodulating circuit 26.

The RF level discriminating circuit 28 detects from the playback datathe signal level decay or rise timing for longer than a pre-set periodto detect the pit P₁ in which is recorded the second data D2L of afrequency range higher than the frequency range of the first data D2U.The RF level discriminating circuit 28 then detects the signal level ofthe reproducing signal Rf at a pre-set timing in the former and latterportions in the track direction as from the lengthwise center in thetrack direction of the pit P₁. The RF level discriminating circuit 28outputs the result of signal level detection DP of the reproducingsignal Rf to the next following bi-level demodulation circuit 30, whichthen verifies the output result of the RF level discriminating circuit28 to detect the playback data of the high frequency range second dataD2L.

With the optical disc of the present embodiment, the result similar tothat of the above-described first embodiment is achieved when the lower2-bit second data D2L is recorded by changes in the pit width W₄ of thepit P₁ of a length not less than a pre-set length to the former andlatter portions of which are each allotted one bit.

(7) Fifth Embodiment

In the optical disc of the present embodiment, the upper 16-bit firstdata D2U of the 18-bit audio data are processed as in the customarycompact disc and thereby recorded as a string of plural pits P₁, whilethe lower 2-bit second data D2L is recorded as the depth P_(D1) of thepit P₁ recorded on the optical disc is varied from its normal depthP_(D). As the pit P₁, the normal depth P_(D) of which is changed by thissecond data D2L, a pit having a duration not less than a pre-set length,such as 5T or longer, is selected, and each 1-bit is allocated andrecorded as the normal depth is changed in the former and latterportions as from the center of the pit P₁.

The optical disc of the present embodiment also is formed using therecording device 1 shown in FIG. 1 and is reproduced using the discreproducing apparatus 20 shown in FIG. 3.

For recording the second data D2L on the second embodiment of theoptical disc, using the recording device shown in FIG. 1, the lightvolume of the laser beam L is controlled, whilst the depth P_(D1) of thepit P₁ is varied from its normal depth by selective light exposure inthe depth-wise direction made possible by resist selection.

By reproducing the optical disc using the disc reproducing apparatusshown in FIG. 3, the audio data DAEx synthesized from the first data D2Uand the second data D2L can be selectively processed to effect audioreproduction with a high sound quality (ExCD sound quality) with afrequency range equivalent to 18 bits.

(8) Sixth Embodiment

In the optical disc of the present embodiment, the upper 16-bit firstdata D2U of the 18-bit audio data are processed as in the customarycompact disc and thereby recorded as a string of plural pits P₁, whilethe lower 2-bit second data D2L is recorded by changes in the width W ofthe pit P₁ corresponding to the length in the direction perpendicular tothe track direction of the pit P₁ recorded on the optical disc. As thepit P₁, the width of which is changed based on the second data D2L, apit P₁ of a length not less than a pre-set length, such as a pit P₁ notless than 5T, is used, and the second data D2L is recorded by changes inthe width of the pit P₁ from the former half to the latter half as fromthe center in the track direction of the pit P₁.

Referring to FIGS. 8A and 8B, the pits P₁ are formed so that, if thelogical level is the logical “1”, the width W6 of the pit P₁ of thesecond data D2L is increased with the lengthwise mid point in the trackdirection of the pit P₁ as a boundary, whereas, if the logical level isthe logical “0”, the width W₅ of the pit P₁ of the second data D2L isdecreased with the lengthwise mid point in the track direction of thepit P₁ as a boundary.

In the recording device 1 for recording data on the present embodimentof the optical disc, as in the first embodiment described above, anerror correction code is appended to the lower 2-bit second data D2L,and the resulting data is interleaved to generate a serial data string.Moreover, the data processing circuit 12 monitors the logical level ofconsecutive bits in the channel data D3 to detect the timingcorresponding to the pit P₁ of not less than the pre-set length, such asnot less than 5T. This data processing circuit 12 allocates each 1 bitdata to the former and latter portions in the track direction of the pitP₁ of not less than the pre-set length to generate and output the lightvolume control data D4.

The RF level discriminating circuit 28 of the disc reproducing apparatus20 for reproducing the optical disc, shown in FIG. 3, performs signalprocessing similar to that performed by the EFM demodulation circuit inthe disc reproducing apparatus exclusively reproducing the customarycompact disc to perform bi-level discrimination of the reproducingsignal Rf, with the channel clocks reproduced from the reproducingsignal Rf as reference, to generate playback data , which is outputtedto the EFM demodulating circuit 26.

The RF level discriminating circuit 28 detects, from the playback data,the timing at which the signal level rises or decays at a period longerthan the pre-set period, to detect the pit P₁ in which is recorded thesecond data D2L of a frequency range higher than the frequency range ofthe first data D2U to detect the signal level of the reproducing signalRf at a pre-set timing before and after the lengthwise center along thetrack of the pit P₁. The RF level discriminating circuit 28 outputs theresult of signal level detection DP of the reproducing signal Rf to thenext following bi-level demodulation circuit 30, which then verifies theoutput result of the RF level discriminating circuit 28 to detect theplayback data of the second data D2L of the high frequency range.

With the optical disc of the present embodiment, it is possible toachieve the results similar to those of the first embodiment if thelower 2-bit second data D2L is recorded by changes in the pit widths W₅,W₆ of pits allocated to the former and latter half portions in the trackdirection of the pit P₁ of a length not less than the pre-set length.

(9) Seventh Embodiment

In the present embodiment of the optical disc, the upper 16-bit firstdata D2U of the 18-bit audio data is processed as in the customarycompact disc, whilst the lower 2-bit second data D2L is recorded bychanges in the depth P_(D) of the pit P₁ recorded on the optical disc.As the pit having its depth changed based on the second data D2L, such apit having a length not less than a pre-set length, such as a pit notless than 5T, is used, and the second data D2L is recorded by changingthe depth from the former to the latter half sides as from the center inthe track direction of the pit.

The pits of the second data D2L are sequentially formed so that, if thelogical level is “1”, the depth P_(D1) of the pit P₁ will be deeper withthe mid portion in the lengthwise direction along the track of the pitas the boundary, whereas, if the logical level is “0”, the depth P_(D1)of the pit P₁ will be shallower with the mid portion in the lengthwisedirection along the track of the pit P₁ as the boundary, as shown inFIG. 9.

The optical disc of the present embodiment can be formed by employingthe recording device 1 shown in FIG. 1, whilst it can be reproducedusing the disc reproducing apparatus 20 shown in FIG. 3.

For recording the second data D2L on the optical disc of the presentembodiment, using the recording device shown in FIG. 1, the light volumeof the laser beam is controlled, whilst the pit depth is changed fromits normal depth by selective light exposure by resist selection.

By reproducing the optical disc by the disc reproducing apparatus shownin FIG. 3, the audio data DAEx, synthesized from the first data D2U andthe second data D2L, can be selectively processed to achieve audioreproduction with the high sound quality (ExCD sound quality) with thebroad frequency range equivalent to 18 bits.

(10) Eighth Embodiment

In the optical disc of the present embodiment, the upper 16-bit firstdata D2U of the 18-bit audio data are processed as in the customarycompact disc and thereby recorded as a string of plural pits P₁, whilstthe pit of the track constituted by the plural pits P₁ recorded on theoptical disc and the lands delimited between these pits P₁ has itslength changed from its normal length in the track direction on the leftand right sides of the track center T₀ as center, to record the seconddata D2L, as shown in FIGS. 10A and 10B.

The pit whose width is changed based on the second data D2L is a pit notshorter than a pre-set length, for example, a pit not less than 5T. Thesecond data D2L is recorded by changes in pit width from the former halfto the latter half portions of the pit as from the center along thetrack. That is, the pit P₁ in which is recorded the second data D2L hasthe length along the track changed on the left and right sides of thetrack direction of the pit P₁, that is on the inner and outer rims ofthe optical disc.

The pits of the second data D2L are formed sequentially so that, if thelogical level is “1”, the inner rim side of the pit is longer in thetrack direction than its outer rim side, as shown in FIG. 10A, whereas,if the logical level is “0”, the outer rim side of the pit is longer inthe track direction than its inner rim side, as shown in FIG. 10B.

In the recording device for recording the second data D2L along with thefirst data D2U on the optical disc, two laser beams L are radiated inthe recording device shown in FIG. 1, these twp laser beams L are on/offcontrolled by respective light modulators, and the two laser beamsoutputted by the light modulator are incident on the master disc 2 andconverged on an objective lens 9 so that the inner rim portion and theouter rim portion in the track direction of the pit P₁ will be exposedto light.

The recording device, adapted for recording not only the first data D2Ubut also the second data D2L on the optical disc, according to thepresent embodiment, appends an error correction code to the second dataD2L and interleaves the resulting data to generate a serial data string.The recording device also on-off controls the two light modulators bythe channel data D3 generated from the first data D2U of the upper 16bits and by the serial data string.

The disc reproducing apparatus, adapted for reproducing the opticaldisc, on which are recorded not only the first data D2U but also thesecond data D2L, by the recording device, illuminates a light beam onthe optical disc and receives the return light beam reflected from theoptical disc by a pre-set photodetector provided on the optical pickup.

Referring to FIG. 11, the photodetector 82 is split in the trackdirection, corresponding to the track extending direction on the opticaldisc, and in a direction perpendicular to the track direction, to definefirst to fourth photodetector portions A to D. The return light beamreflected from the optical disc forms a beam spot 88 about the point ofintersection of divison lines of the first to fourth photodetectorportions A to D as center.

The photodetector 82 outputs detection outputs SA to SD detected by thefirst to fourth photodetector portions A to D. The disc reproducingdevice, having an optical pickup including this photodetector 82 andadapted for reproducing the optical disc according to the presentinvention, processes the detection outputs SA to SD, as detected by thefirst to fourth photodetector portions A to D, with current to voltageconversion, and performs processing operations to generate reproducingsignal Rf etc. This disc reproducing device sums the detection outputsSA to SD, outputted by the first to fourth photodetector portions A toD, by a first adder circuit 83, to generate reproducing signal Rf, andprocesses the reproducing signal Rf in the same way as the customarydisc reproducing device used exclusively for reproducing the compactdisc to reproduce the upper 16-bit first data D2U recorded by a stringof plural pits.

The disc reproducing device according to the present invention includes,in addition to the first adder circuit, second and third adders 84, 85,as shown in FIG. 11. These second and third adders 84, 85 sum detectionoutputs SA and SB as detected by the first and second photodetectorportions SA, SB and detection outputs SC and SD as detected by the thirdand fourth photodetector portions SC, SD to produce the results ofaddition SA+SB and SC+SD which are subjected to subtraction in asubtraction circuit 86. By this signal processing, the disc reproducingdevice for reproducing the optical disc according to the presentinvention generates a reproducing signal RFD (SA+SB−SC−SD), the signallevel of which is changed responsive to the shape of the pit P₁ whoseinner rim side shape is changed and to the shape of the pit P₁ whoseouter rim side shape is changed, among the pits the lengths of which inthe track direction on left and right sides of a track have been changedbased on the second data D2L of the lower two bits. If the signal levelof the reproducing signal RFD is changed to more than a pre-set extent,the reproducing signal RFD is bi-level-discriminated at a timing atwhich the reproducing signal RFD is produced from the site of differentshapes of the pits P₁ on the inner and outer rim sides, and thebi-level-discriminated signal is processed to produce playback dataderived from the second data D2L and which is of a higher frequencyrange than the frequency range of the first data D2U.

In this optical disc, the audio data DAEx synthesized from the firstdata D2U and the second data D2L is selectively processed to achieveaudio reproduction of a high sound quality having the frequency rangeequivalent to 18 bits.

(11) Ninth Embodiment

In this optical disc, the first data D2U of the upper 16 bits of the18-bit audio data is processed in the same way as the customary compactdisc to form a string of plural pits P₁, which is recorded. The seconddata D2L is recorded by changing the lengths of the plural pits P₁ andlands R₁ recorded on the optical disc in the direction of left and righttracks about the track center T₀ as center from the normal lengths basedon the second data D2L. The lands R₁ are defined between the pits P₁recorded on the optical disc. In this case, the lengths of the inner andouter rims of the pits P₁ and lands R₁ in the track direction of theoptical disc are changed in a specified channel bit. In the presentexample, this specified channel bit is set at a center bit B_(c1) of theconnecting bits B_(c) to change the shape of the pit P₁ and that of theland R₁ by the connecting bits on the inner and outer rim sides on theleft and right sides of the track center T0. The 14 channel bits,between the connecting bits B_(c), to which are allotted the first dataD2U of the upper 16 bits, are not affected by the recording of the lower2 bits of the second data D2L, and may be reproduced with phaseallowance and amplitude allowance comparable to those in the customarycompact disc.

For recording the first data D2U and the second data D2L on the opticaldisc, the recording device 1 on/off controls the three laser beams,obtained on separating the laser beam L outputted by the recording laser5, shown in FIG. 1, by respective light modulators 6, and converges thethree laser beams, outputted by the light modulator 6, on the masterdisc 2 by the objective lens 9. These three light beams are allotted tothe center of each pit, with the track center T₀ as center, and to theinner and outer sides of the optical disc, which are on the left andright sides of the track center T₀.

The recording device 1 also on/off controls the laser beam allotted tothe center of the pit P₁, by the channel data D3 generated by the upper16-bit first data D2U, to record the upper 16-bit first data D2U byrepetition of strings of plural pits P₁.

The recording device 1 also appends an error correction code to thesecond data D2L and interleaves the resulting data to form a serial datastring, and outputs the laser beam allotted to the inner or outer rimsides of the pit P₁, responsive to the logical level of the serial datastring, at a timing of the center bit B_(c1) of the connecting bits Bcin the channel data D3, whereby, if the pit P₁ associated with the firstdata D2U is formed astride the connecting bits B_(c), as shown in FIG.12A, the master disc 2 is exposed to light in such a manner that,responsive to the logical level of the first data D2U, the width W₂₁ ofthe pot P₁ will be changed appreciably towards the inner and outer rimsides, at a portion corresponding to the center bit B_(c1) of theconnecting bits B_(c), as shown in FIGS. 12B-1 and 12B-2.

In a case wherein the pit P₁ continues to the center B_(c1) of theconnecting bits B_(c), the master disc 2 is exposed to light so that thewidth W₂₁ of the pit P₁ will be increased towards the inner or outer rimat the trailing end in the track direction of the pit P₁ associated withthe center bit B_(c1) of the connecting bits B_(c), depending on thelogical level of the second data D2L, as shown in FIGS. 12C-1 and 12C-2.In a case wherein the pit P₁ is started as from the center B_(c1) of theconnecting bits B_(c), the master disc 2 is exposed to light so that thewidth W₂₁ of the pit P₁ will be increased towards the inner or outer runat the leading end in the track direction of the pit P₁ associated withthe center bit B_(c1) of the connecting bits B_(c), depending on thelogical level of the second data D2L, as shown in FIGS. 12D-1 and 12D-2.

In a case wherein the center bit B_(c1) of the connecting bits B_(c) isallotted to the land R, the master disc 2 is exposed to light so that,responsive to the logical level of the second data D2L, a pit P_(c1)having width corresponding to the increased width W₂₁ of the pit P₁ willbe formed, as shown in FIGS. 12E1 and 12E-2.

The disc reproducing apparatus, adapted for reproducing the opticaldisc, having the first data D2U and the second data D2L recorded thereonas described above, performs selective bi-level discrimination of thereproducing signal RFD, obtained using the photodetector 82 shown inFIG. 11, at a timing the light beam radiated from the optical pickupscans the center bit B_(c1) of the connecting bits B_(c), to generateplayback data of a frequency range higher than that of the first dataD2U derived from the lower 2-bit second data D2L.

With the present optical disc, it is similarly possible to achieve audioreproduction with the high sound quality (ExCD sound quality) of a broadfrequency range equivalent to 18 bits by selective processing of theaudio data DAEx synthesized from the first data D2U and the second dataD2L.

Moreover, by setting a specified channel bits at the connecting bitsB_(c) and by setting it at the center bit B_(c1) of the connecting bitsB_(c), the 14 channel bits, between the connecting bits B_(c), to whichare allotted the upper 16 bit first data D2U of the 18-bit audio data,are not affected by the recording of the lower 2 bits of the second dataD2L, and may be reproduced with phase allowance and amplitude allowancecomparable to those in the customary compact disc.

(12) Tenth Embodiment

With the optical disc of the present embodiment, as with the opticaldisc s of the above-described respective embodiments, the upper 16-bitfirst data D2U of the 18-bit audio data are processed as in thecustomary compact disc so as to be recorded as plural bits. On the otherhand, the lower 2-bit second data D2L are recorded by the forward andrear portions in the lengthwise direction thereof in the track directionof the pit P₁ are offset in a direction perpendicular to the trackdirection with the track center T₀ in-between. If, in the presentembodiment of the optical disc, the logical level of the second data D2Lis the logical “0”, the forward side of the pit P₁ is offset towards theouter rim of the optical disc in a direction perpendicular to the trackdirection from the track center T₀, with the center of the pit in thelengthwise direction thereof in the track direction as a boundary,whilst the rear end of the pit P₁ is offset towards the inner rim of theoptical disc from the track center T₀ in a direction perpendicular tothe track direction, as shown in FIG. 13A. On the other hand, if thelogical level of the second data D2L is the logical “1”, the forwardside of the pit P₁ about the center in the lengthwise direction thereofin the track direction as a boundary is offset towards the inner rim ofthe optical disc in the direction perpendicular to the track directionfrom the track center T₀, whilst its rear portion is offset towards theouter rim of the optical disc in a direction perpendicular to the trackdirection towards the track center T₀.

For preparing an optical disc in which the forward and rear portions ofthe pit P₁ formed based on the first data D2U in the lengthwisedirection thereof in the track direction are offset in the directionperpendicular to the track direction with the track center T₀ in-betweenthe radiating direction of the laser beam L is deflected by a lightdeflector 6 arranged on the optical path of the laser beam L outputtedby the light modulator 6 of the recording device 1 shown in FIG. 1 at atiming at which the pit P₁ is offset by the lower 2-bit second data D2L.The light modulator may be an electro-acoustic optical element.

At this time, the second data D2L is phase-modulated to drive the lightmodulator 6 to split one of the bits of the second data D2L into twochannels, the logical levels of which are set in meeting with theoffsetting of the pit P₁, as shown in FIGS. 13A and 13B.

The amount of the offset of the pit P₁ in the direction perpendicular tothe track direction is set so that the tracking control in reproductionwill not be affected by the offsetting of the pit P₁ and so that theupper bit side first data D2U will be reproduced with sufficient phaseallowance and sufficient amplitude allowance.

In reproducing the optical disc, the second data D2L recording by theoffsetting of the pit P₁ is reproduced using the output signal RFDobtained from the photodetector 82 provided on the optical pickup of thedisc reproducing apparatus as shown in FIG. 11, or using the high rangesignals of the tracking error signals.

With the optical disc of the present embodiment, even in a case whereinthe pit P₁ formed based on the first data D2U is offset in the directionperpendicular to the track direction so that the width of the pitdiffers in the forward and rear portions in the lengthwise directionthereof in the track direction with the track center T₀ in-between, bythe lower 2-bit second data D2L, it is possible to synthesize the firstdata D2U and the second data D2L to achieve audio reproduction of highsound quality (ExCD sound quality) of the broad frequency rangeequivalent to 18 bit sound quality.

(13) Eleventh Embodiment

If, in the optical disc of the present invention, the length in thetrack direction of the pit P₁ is varied from its normal length to recordthe second data D2L, two edges of the pit P₁ are necessarily present ina codeword made up of 14 channel bits, to which is allotted 1 byte(8-bit) audio data, under the modulation rule of the EFM modulation, asshown in FIG. 5. This modulation rule of the EFM modulation is based onthe format of the customary compact disc. In such case, the 2-bit seconddata D2L may be allotted to each codeword.

Meanwhile, if the 1-bit second data D2L is allotted to the sole pit P₁by the width of the pit P₁ as the length in the direction perpendicularto the track direction, or by the depth of the pit P₁, two pits P₁ arenot necessarily allotted to a sole codeword, depending on the EFMmodulation rule. In such case, it is difficult to allot the second dataD2L of 2 bits to each codeword.

In such case, the second data D2L is allotted to the pits P₁ so that theupper bit first data D2Uand the lower bit second data D2L are associatedwith each other, with a pre-set block as a unit.

Specifically, with the format of the customary compact disc, connectingchannel bits and code words are arrayed in succession to the 22 channelclock frame sync so that each frame is formed by 588 channel clocks. ACD frame is formed by a concatenation of these frames. Thus, in a framecomprising 588 channel clocks, or in a CD frame, the second data D2L issequentially allotted to the respective pits, so that the upper bitfirst data D2Uand the lower bit second data D2L will be in meeting witheach other.

In the recording device for preparing the optical disc, the second dataD2L is buffered in an amount corresponding to at least 588 channelclocks or to a CD frame, and is sequentially outputted at a pit-formingtiming to vary the normal pit length in the track direction. Also, withthe disc reproducing apparatus, the reproduced second data D2L isbuffered, with the sync frame or sub-code as a reference, and isoutputted at a timing of the associated upper bit first data D2U, forprocessing.

With the present optical disc, in which the upper bit first data D2U issplit on the block basis for recording, and the lower bit second dataD2L is allotted to the pits of the associated block, on the block basis,the lower bit second data D2L is recorded even if the two pits are notnecessarily allotted to each codeword under the modulation rule, wherebyit is possible to synthesize the first data D2U and the second data D2Lto achieve audio reproduction of high sound quality equivalent to 18-bitsound quality.

(14) Twelfth Embodiment

In the optical disc of the present embodiment, a sole codeword by 14channel bits is split at a pre-set bit cell boundary, and the seconddata D2L is recorded as the forward and rear portions in the lengthwisedirection of the pit in the track direction are offset in the directionperpendicular to the track direction, with the track center T₀in-between, as shown in FIGS. 14A and 14B.

For recording the lower bit second data D2L, the pit P₁ is split into aforward portion and a rear portion in the track direction with thecenter bit cell in the lengthwise direction thereof in the trackdirection and each one bit of the second data D2L is allotted to thesplit region, whilst the 2-bit second data D2L is allocated to each codeword.

If, in this optical disc two bits P₁ re allotted to e.g., a code word sothat the associated second data D2L will be allotted to each code word,it is necessary that one of the pit P₁ ceases to be deformed.

With the present optical disc, in which a code word is split at apre-set bit cell boundary, and the forward and rear portions of thelengthwise direction of each pit P₁ in the track direction, with the bitcell boundary as a boundary, are offset in a direction perpendicular tothe track direction on both sides of the track center T₀, plural bits ofthe lower bit second data D2L can be allotted to a sole pit forcorrespondingly improving the recording density of the second data D2L.

Moreover, each codeword may be associated with the second data D2L forcorrespondingly simplifying the processing of the recording andreproducing system.

(15) Other Embodiments

In the foregoing description, the lower bit second data D2L are recordedby changing the width, depth, length in the track direction or length inthe direction perpendicular to the track direction, of the pit,differentially deforming the inner and outer rims in the track directionof the pit, or differentially offsetting the forward and rear portionsin the track direction of the pit in the direction of the inner andouter rims of the disc. The present invention is, however, not limitedto these embodiments since these embodiments may be used in combination.By so doing, the data volume that can be allotted to each bit may beincreased, while the error correction code appended to the second dataD2L can be intensified and the recording and/or reproduction of thesesorts of data can be improved in reliability. Moreover, the audio dataimproved in the number of bits or data volume can be recorded. In thiscase, the second data D2L associated with a code word can be allotted toplural bits to simplify the processing of the recording and reproducingsystems.

In the foregoing description, the lower bit second data D2L are recordedby changing the width, depth, length in the track direction or length inthe direction perpendicular to the track direction, of the pit,differentially deforming the inner and outer rims in the track directionof the pit, or differentially offsetting the forward and rear portionsin the track direction of the pit in the direction of the inner andouter rims of the disc. The present invention is, however, not limitedto this configuration and may be applied to the recording by multiplevalues. That is, in comparison with FIGS. 13A and 13B, it will be seenthat, if a pit P₁ having the forward side and the rear side with thelengthwise mid portion thereof in the track direction as a boundaryoffset towards the outer and inner rims of the disc, respectively, fromthe track center T₀ in a direction perpendicular to the track direction,a pit P₀ not offset as shown in FIG. 15B and a pit P₁ having the forwardside and the rear side with the lengthwise mod portion thereof in thetrack direction as a boundary offset towards the inner and outer rims ofthe disc, respectively, from the track center T₀ in the directionperpendicular to the track direction, are combined together to enableplural bits of the lower bit second data D2L to be recorded with threevalues. Even with such multi-valued recording, plural bits of the seconddata D2L can be allotted to a codeword to simplify the processing of therecording and reproducing systems correspondingly.

In the foregoing description, an error correction code is allotted tothe lower 2-bit second data D2L, in association with the processing ofthe upper 16-bit first data D2U, and the resulting data is interleaved.The present invention is, however, not limited to this configurationsince the second data D2L can be processed and recorded by processingdifferent from that described above.

In the foregoing description, when the lower bit second data D2L arerecorded by changing the width, depth, length in the track direction orlength in the direction perpendicular to the track direction, of thepit, differentially deforming the inner and outer rims in the trackdirection of the pit, or differentially offsetting the forward and rearportions in the track direction of the pit in the direction of the innerand outer rims of the disc, the second data D2L is modulated in phase.However, phase modulation may also be used when the second data D2L isrecorded based on the different between the inner and outer rims of thepit.

In the foregoing description, the inner and outer rims of the pit areoffset at the center bit of the connecting bits, as a specified channelbit. However, the present invention is not limited thereto since theleading or trailing bit of the connecting bits, or one of the 14 channelbits, to which the first data D2U are allotted, may be used as thespecified channel bit. In this case, plural bits of the second data D2Lmay be allotted to a single connecting bit or a single bit of the 14channel bits, as appropriate.

In the foregoing description, the inner and outer rims of the pit areoffset at the center bit of the connecting bits, as a specified channelbit. However, the present invention is not limited thereto since thesecond data D2L may be recorded by varying the pit width or depth at aspecified channel bit. In such case, the second data D2L may be allottedto a sole connecting bit or to plural bits of a sole 14-channel bits.

In the foregoing description, the lower 2-bit second data D2L of the18-bit audio data is deformed, along with the error correction code,with the pits derived from the first data D2U of the upper 16 bits. Thepresent invention is, however, not limited to this configuration sinceall or part of the error correction code may be allotted to thesub-code.

Also, in the foregoing description, 18-bit audio data are recorded as itis split into upper 16 bits and lower 2 bits. However, the presentinvention is not limited to this embodiment since it may be broadlyapplied to a case of splitting the audio data of a variable number ofbits to upper and lower order bits.

Moreover, in the foregoing description, desired audio data are recordedby pits and lands. The present invention is, however, not limited tothis configuration since the present invention may be broadly applied toa magneto-optical disc or a magneto-optical disc recording and/orreproducing apparatus for recording audio data by repetition of marksand spaces.

The present invention also is not limited to recording the audio data onan optical disc since the present invention may be broadly applied torecording video data on an optical disc.

(16) Further Embodiments

In the above-described embodiments, the second data D2L is recorded byvarying the length of pits of a track, constituted by the plural pits P₁corresponding to the first data D2U, and the lands R₁ defined betweenthese pits, along the entire length thereof in the track direction, byvarying the width of the pits as a length in a direction perpendicularto the track direction, and by varying the width of the pits as from amid portion towards the forward or rear end of the pit. Alternatively,the second data D2L may be recorded by setting the length of the pit P₂at a mid portion thereof in the track direction T thereof, that is awidth W₁₁, to a width W₁₂, narrower than the length thereof in the trackdirection T, that is the normal width W₁₁, as shown in FIG. 16. Stillalternatively, the second data D2L may be recorded by forming a recess51 shallower in depth than the normal pit P₁, as shown in FIG. 15.

The pit P₂ of the second data D2L, recorded by varying the width W₁₁ ata mid portion thereof in the track direction T in the directionperpendicular to the track direction T, is of a period not less than 5T,whereas the land R₁ of the second data D2L, recorded by forming therecess 51 shallower in depth than the normal pit P₁, may also be of aperiod not less than 5T.

By recorded the second data D2L by the pit P₂ with a period not lessthan 5T, it is possible to read out the second data D2L with asufficient detection output as the detection output of the first dataD2U recorded by the pit P₂ is prevented from being decreased.

The reproduction, that is reading, of the second data D2L, ishereinafter explained.

The reproducing signal outputted from the RF circuit 24 of FIG. 1,corresponding to the pit P1 having the normal width W₁₂ and the land R₁not provided with the recess 51, is the reproducing signal Rf1, havingthe regular amplitude, as shown in FIG. 17, whereas the reproducingsignal corresponding to the pit P₂ having a narrow width W₁₁ and theland R₁ having the recess 5 1, is the reproducing signal Rf2 smaller inamplitude than the reproducing signal Rf1.

In the present embodiment, in which the lengths of the pit P₂ and theland R₁, carrying the second data D2L, are of a period not less than 5T,it is unnecessary to normalize the reproducing signal Rf in the RF leveldiscriminating circuit 28 of FIG. 1, so that the reproducing signal Rffrom the RF circuit 24 is directly supplied to the bi-level demodulationcircuit 30. The bi-level demodulation circuit 30 has two thresholdvalues, for example, a threshold value TH₂ as an intermediate levelbetween the reproducing signals Rf1, Rf2 corresponding to the land R₁having the recess 51 and to the land R₁ not having the recess 51, and athreshold value TH₃ at an intermediate level between the reproducingsignals Rf1, Rf2 corresponding to the pits P₁, P₂, respectively. Thebi-level demodulation circuit 30 discriminates the reproducing signal Rfoutputted by the RF circuit 24, based on the threshold value TH₂, toreproduce the second data D2L. The bi-level demodulation circuit 30 alsodiscriminates the reproducing signal Rf, based on the threshold valueTH₃, to reproduce the second data D2L recorded on the pit P₂.

(17) Further Embodiments

In the above-described embodiments, the second data D2L is recorded asaudio data of the high frequency range as supplementary data to thefirst data D2U not contained in the upper 16-bit first data D2U of audiodata DA as 18-bit parallel digital data. However, data concerning thefirst data D2U is used as the second data D2L.

For example, if the first data D2U is the 2-channel audio data, thesecond data D2L may be the audio data constituting multi-channel audiodata as a portion of the first data D2U. The second data D2L used hereis data inputted to a speaker arranged at the front side center of themulti-channel data or a speaker arranged above the listener's head ordata inputted to left and right speakers on the back side.

The second data D2L may be data recorded as multi-channel audio dataindependent from the first data D2U.

If the first data D2U is the audio data of a musical number includingthe lyrics, the second data D2L is recorded as data corresponding to theperforming portion of this musical number. By recording the first dataD2U and the second data D2L, it is possible to selectively reproduceonly the performing potion of a musical number including the lyric, thusrealizing variegated audio reproduction.

As the second data D2L, copyright data for protecting the copyright byimposing limitations on duplication of the first data D2U recorded asdigital data may be recorded.

If, when the first data D2U is encrypted, the second data D2L isrecorded as key a data for decrypting the first data D2U, it is possibleto inhibit free reproduction or duplication of the first data D2U toassure reliable protection of the work corresponding to the first dataD2U.

The second data D2L may also be management data indicating that thesupplementary data relevant to the first data D2U has been recorded withsignal compression.

The second data D2L may be recording with signal compression withvariable formats in areas totally independent of the area in which torecord the second data D2L.

In an inner run area of an optical disc 101, having the second data D2Lrecorded thereon along with the first data D2U, there is provided alead-in area 102 in which to record TOC (table-of-contents) dataindicating the contents of data recorded on the optical disc 191. Afirst data recording area 103 is provided on an outer rim side of thelead-in area 102 and a second data recording area 104 is provided on theouter rim area of the first data recording area 103.

In the first data recording area 103, there is recorded audio data in aformat of the customary compact disc, whereas, in the second datarecording area 104, there is recorded audio data capable of realizingaudio reproduction of optimum sound quality. This audio data includeseven the audio data of high frequency range not contained in the audiodata recorded in the first data recording area 103 with signalcompression afforded by a variety of signal compression means.

If data recorded in the second data recording area 104 is such data asfee charging, this data is the first data D2U, while plural bits formedbased on the first data D2U is deformed based on the encryption data asthe second data D2L and recorded. By recording the encryption data asthe second data D2L, it is possible to inhibit free reproduction orduplication of the data recorded in the second data recording area 104to assure reliable protection of the work derived from the second dataD2L.

In this case, data for decoding the encrypted data is recorded in thelead-in area 102. This data is recorded by deforming the plural pitsformed based on the TOC data based on the data used for decrypting theencrypted data.

The data recorded in the second data recording area 104 need notnecessarily be a unit of audio data, since a variety of data such asdata constituting the multi-channel audio data may be recorded alongwith the data recorded in the first data recording area.

By not recording supplementary data in the pits formed based on datarecorded in the first data recording area 103, it is possible tomaintain high data quality of data recorded in the data recording area103.

The pits formed in the lead-in area 102 may be deformed by second dataindicating the presence of the second data recording area 104 forrecording.

INDUSTRIAL APPLICABILITY

According to the present invention, as described above, since the pluralpits of a track constituted by plural pits formed based on first data tobe recorded and lands between the pits are deformed based on the seconddata and the deformed pits are recorded, high-quality audio reproductionmay be achieved. Moreover, variegated audio reproduction may be achievedby suitably synthesizing or selecting the first and second data forreproduction.

What is claimed is:
 1. An optical recording medium comprising: a track constituted by a plurality of pits formed based on first data recorded therein and lands defined between said pits; wherein said plurality of pits are deformed from a regular shape thereof as formed on said optical recording medium based on second data; said deformation of said plural pits includes a plurality of widths across at least one of said plurality of pits, said plurality of widths being measured in a direction perpendicular to a direction of said track; and a length of left and right portions of said deformed pits on both sides of a track center in said track direction is varied from a regular length thereof based on said second data, said length of said left portion and said length of said right portion being unequal.
 2. The optical recording medium according to claim 1, wherein the length in the track direction of said pits is varied, based on said second data, from the regular length thereof in the track direction as formed on the optical recording medium.
 3. The optical recording medium according to claim 1, wherein the depth of said pits is varied, based on said second data, from the regular depth thereof as formed on the optical recording medium.
 4. The optical recording medium according to claim 1, wherein at least a portion of the length in a direction perpendicular to the track direction of said pits is varied, based on said second data, from the regular length thereof in the direction perpendicular to the track direction as formed on the optical recording medium.
 5. The optical recording medium according to claim 4 wherein the length in a direction perpendicular to the track direction of a given pit having a pre-set length is varied, based on said second data, from the regular length thereof in said direction perpendicular to the track direction as formed on the optical recording medium.
 6. The optical recording medium according to claim 5 wherein the length of said pits in a direction perpendicular to the track direction at a mid portion thereof in said track direction is smaller than the length of other portions of said pits in said track direction.
 7. The optical recording medium according to claim 5 wherein the length of said pits in a direction perpendicular to the track direction is varied, based on said second data, at forward and rear portions thereof in said track direction.
 8. The optical recording medium according to claim 4 wherein the depth of said pits is further varied, based on said second data, from the regular depth thereof as formed on the optical recording medium.
 9. The optical recording medium according to claim 1, wherein the forward and rear portions of said pits in said track direction are offset, based on said second data, in a direction perpendicular to said track direction with said track center in-between.
 10. An optical recording medium including a data recording area having a spirally extending track constituted by a plurality of pits formed based on first data recorded therein and lands defined between neighboring pits, and a management data area for recording therein management data for said first data recorded in said data recording area, wherein at least said plurality of pits recorded in said management area are deformed from a regular shape thereof as formed on said optical recording medium based on said second data; said deformation of said plurality of pits includes a plurality of widths across at least one of said plurality of pits, said plurality of widths being measured in a direction perpendicular to a direction of said track; and a length of left and right portions of said deformed pits on both sides of a track center in said track direction is varied from a regular length thereof based on said second data, said length of said left portion and said length of said right portion being unequal.
 11. The optical recording medium according to claim 10, wherein the length in the track direction of said pits is varied, based on said second data, from the regular length thereof in the track direction as formed on the optical recording medium.
 12. The optical recording medium according to claim 10, wherein the depth of said pits is varied, based on said second data, from the regular depth thereof as formed on the optical recording medium.
 13. The optical recording medium according to claim 10, wherein at least a portion of the length in a direction perpendicular to the track direction of said pits is varied, based on said second data, from the regular length thereof in a direction perpendicular to the track direction as formed on the optical recording medium.
 14. The optical recording medium according to claim 13 wherein the length in a direction perpendicular to the track direction of a given pit having a pre-set length is varied, based on said second data, from the regular length thereof in said direction perpendicular to the track direction as formed on the optical recording medium.
 15. The optical recording medium according to claim 14 wherein the length of said pits in a direction perpendicular to the track direction at a mid portion thereof in said track direction is smaller than the length of other portions of said pits in said track direction.
 16. The optical recording medium according to claim 14 wherein the length of said pits in a direction perpendicular to the track direction is varied, based on said second data, at forward and rear portions thereof in said track direction.
 17. The optical recording medium according to claim 13 wherein the depth of said pits is further varied, based on said second data, from the regular depth thereof as formed on the optical recording medium.
 18. The optical recording medium according to claim 10, wherein the forward and rear portions of said pits in said track direction are offset, based on said second data, in a direction perpendicular to said track direction with said track center in-between.
 19. The optical recording medium according to claim 10 where in said first data is digital data recorded on said optical recording medium and wherein said second data is supplementary data to said digital data.
 20. The optical recording medium according to claim 19 wherein said supplementary data is data at least including copyright data.
 21. The optical recording medium according to claim 10 wherein said first data is upper bits of digital data recorded on said optical recording medium and wherein said second data is lower bits of said digital data.
 22. The optical recording medium according to claim 10 wherein discriminating data indicating whether or not said second data is recorded on the optical recording medium is recorded in said management data area.
 23. The optical recording medium according to claim 10 wherein said first data is encrypted data and said second data is key data for decrypting said first data.
 24. The optical recording medium according to claim 10 wherein said first data is 8-14 modulated data. 